joining walls

[DerekvG]

I have a problem joining walls

I can join the endpoints of a N-S wall perpendicular to an E-W wall
which works fine for outer walls...
however i cannot join a piece of inner wall to the joined corner of a NSwll and an EW wall
I also have trouble joining inner walls to the middle of a outer wall becauas iḿ left with half an outer wall joined to the inner wall

[Puybaret]

A wall can be joined only at each of its ends to another wall.